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1. Field of the Invention
The apparatus of the present invention relates to jarring tools used in downhole drilling. More particularly, the present invention relates to an improved apparatus for jarring stuck tools, including pipe, downhole and a method of achieving same.
2. General Background of the Invention
In the art of drilling wells for recovery of hydrocarbons, the process incorporates a drill string which comprises a plurality of threaded tubular members such as drill pipe being approximately 30 foot each in length, the drill pipe threaded end to end which is then used to rotate the drill bit either from the surface or through the use of a drill motor which would rotate the bit without the rotation of the drill pipe itself. Often times during that process, the drill string will become lodged at a certain point along its length within the borehole.
In the efforts to dislodge the drill pipe or other tools lodged downhole, a type of tool known as a jarring tool would be used in such an attempt. In the current state of the art, jarring tools as they currently utilize may be used to either jar the stuck or the lodged portion of pipe either in the up or down direction, depending on the makeup of the tool. In most cases, it would be more desirable to jar down on the pipe than to jar up. The reason for this is that drill pipe will usually get lodged when it is being pulled up as opposed to being moved downward, so jarring downward will more likely free the pipe. In such a case, the pipe is probably wedged against an obstruction caused by the upper movement of the pipe, and jarring upward may tend to wedge the debris around the section of pipe even tighter.
Methods of downward jarring which are currently used in the art includes applying compression on the drill string to which a down jar has been attached, whereby the jar releases at a pre-set load, allowing the hammer of the jar to freely travel a short distance impacting the anvil of the tool, delivering a downward blow. The effectiveness of this method has limitations, due to compressional buckling of the drill string, as well as drag. Therefore, it is often difficult to achieve a large downhole jarring force in a vertical well, and the problem is exacerbated in the horizontal portion of a directional drilling operation. A jar in the upward direction can be attached to the top of the stuck pipe or tool, and the jar can be pulled upward until it is tripped. While this type of jarring can produce more force than downward jarring, it is typically in the wrong direction for most instances of stuck pipe.
Certain patents have been obtained which address the method of jarring pipe loose from a borehole, and these will be provided in the prior art statement submitted herewith.
The apparatus of the present invention solves the problems in the art in a simple and straight forward manner. What is provided is an apparatus for jarring a portion of drill string lodged within a borehole, by jarring downward using tension versus compression. The apparatus would include a first member for attaching a first lower end of the apparatus to the upper end of the lodged tool or pipe through a threadable attachment; there would then be provided a second member for attaching a second end of the apparatus to a drill string on its upper end portion; there is further provided a third anvil or hammer member which is triggered by a spring having stored compressional force transferred by tension from the drill string to the apparatus when the drill string is pulled upward. There is also provided an actuator for rapidly releasing the tension force provided by the spring downward onto the stuck pipe in order to provide an impacting, downward force onto the pipe in an effort to dislodge the pipe. There is further provided a slow release mechanism for slowly releasing the tension force stored by the spring.
Therefore, it is the principal object of the present invention to provide a tool for dislodging drill pipe down a borehole, which provides for a downward jarring on the stuck pipe or tool to facilitate dislodging of same;
It is another principal object of the present invention to provide an apparatus for dislodging pipe or tools from a borehole by imparting a downward force, yet disallowing the weight of the hammer member from imparting additional, undesirable force on the surface mechanisms;
It is a further object of the present invention to provide a jarring tool which has an internal mechanism for regulating the amount of force that is imparted onto the stuck object lodged within the borehole, yet provides for sufficient force to dislodge the pipe or tool within the borehole;
It is a further object of the present invention to provide a method of dislodging tools stuck down a borehole which includes providing a tool having a first portion secured to the lodged tool, a second portion secured to the tubing above the tool, and a third portion defining a means for imparting jarring force against the stuck tool, while moving independently of the second portion to prevent undesired force on the elements above the tool.